Workers will return to Ford's engine plant at Bridgend today for the first time since being told the factory is to close next year with heavy job losses.
Production at the Bridgend factory will end in September 2020 when a contract to build engines for Jaguar Land Rover (JLR) comes to an end.
Ford last week blamed the closure on the end of the JLR contract as well as falling demand for engines built at Bridgend. Workers were sent home after receiving the news on Thursday and told to return on Monday.
On Monday ministers from the UK and Welsh governments will discuss details of a task force, involving local authorities and trade unions, which is being set up to look at ways of creating jobs to replace those lost at Bridgend.
Around 1,700 workers are employed at the factory, but scores of firms supply goods and services to the site.
Member of Parliament for Bridgend, Madeleine Moon, described the decision as "devastating" and added "I'm told there's about 12,000 jobs in the supply chain".
Delegates at the GMB's annual conference in Brighton urged Ford to reconsider its decision. They also called on the UK and Welsh governments to work with unions to save the factory and prevent another "nail in the coffin" of manufacturing.
Welsh delegate Jennifer Smith told the conference that the closure was a "body blow" to the entire Welsh economy.
Workers were sent home early on Thursday after the decision was confirmed by Ford:
Despite Ford denying the decision had anything to do with Brexit, she said it must have been a factor, especially following the recent EU election results and the likelihood of a new Tory party leader being in favour of leaving the EU without a deal.
She also accused Ford of failing to invest in engines for the future and of "abandoning" Bridgend's highly skilled workforce.